Wireless communication systems are widely used to provide voice and data services for multiple users using a variety of access terminals such as cellular telephones, laptop computers and various multimedia devices. Such communications systems can encompass local area networks, such as IEEE 801.11 networks, cellular telephone and/or mobile broadband networks. The communication system can use a one or more multiple access techniques, such as Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Code Division Multiple Access (CDMA), Orthogonal Frequency Division Multiple Access (OFDMA), Single Carrier Frequency Division Multiple Access (SC-FDMA) and others. Mobile broadband networks can conform to a number of system types or partnerships such as, General Packet Radio Service (GPRS), 3rd-Generation standards (3G), Worldwide Interoperability for Microwave Access (WiMAX), Universal Mobile Telecommunications System (UMTS), the 3rd Generation Partnership Project (3GPP), Evolution-Data Optimized EV-DO, or Long Term Evolution (LTE).
In wireless communication systems, the desired signal level as well as the interference level fluctuates in time due to temporal fading. In systems where multiple users share the same time slot or frequency bandwidth, highest performance is achieved when transmissions occur when the desired signal level is high and the interference level is low. This happens as naturally in downlink transmissions for some systems, such as LTE that are configured to have a user terminal transmit a latest C/I value to the base station. In noise limited systems, the C/I value is highest when the desired signal is at the highest level and the interference is at the lowest level. The LTE base station, therefore, assigns a user terminal a given resource block (RB), when the C/I is relatively high using a certain priority criterion. Since transmitting stations are typically stationary, the reason for the fluctuation of C/I is the temporal fading of the desired and interference signals. However, measurement error and the delay in reporting (feedback delay) may result in the transmitting stations not transmitting at the best times with respect to temporal fading. For a slow moving or stationary user terminal, the prediction error due to the feedback delay of the C/I measurement is negligible and only measurement error is the issue. In LTE, a 40-80% capacity improvement can be obtained applying this technique if there are greater than about 20 user terminals per sector.
In an uplink channel, however, interference is unpredictable because mobile user terminals are moving with respect to each other, and because resource blocks are constantly being reassigned. A C/I measurement taken at one instant is often invalid a short time later because of the fast changing multipath environment and the change of the transmitter, which is in this case, is the UE. It is, therefore, very difficult for conventional communication systems to efficiently schedule transmissions to match signal and interference fading of the multipath environment.